Conventionally, as a polymerization method for a polymer comprising a polyvinyl ether structure, a polymerization method by living cationic polymerization has been known (see, for example, Japanese Unexamined Patent Application Publication Nos. H11-080221A and 2007-099881).
The cationic polymerization described in Japanese Unexamined Patent Application Publication Nos. H11-080221A and 2007-099881 and the like generally requires effort to adjust reaction conditions (particularly, temperature conditions), and is known to have problems such as expensive catalysts and difficult preparation in water-based media.